Drafting instrument



c. F. GOLDEN.

DRAFTING INSTRUMENT;

FILED JULY 20. 1922. 2 SHEETS- SHEET 1.-

I i: llll T 0 all whom it may concern:

Patented Mar. 6, 1923.

v U it CHARLES rnnivion'r GOLDEN, oessavsamsmm,

nnsrrme rnsrnniunn r.

Application filed. July 20,1922 Serial K0357633 1.

means for holding the instrument on a blackboard, the suction means being housed,

and the hou'singfor the suction means constituting an important reinforcement for the instrument, the suction means being so-located that it will form a useful guide' for placing the instrument at the right'place, approximately on the blackboard.

It is within the province of the disclosure to improve generallymnd to enhance the utility of devices of that type to which the invention apperta ins.

With the above and other objectsin view, which: will appear as the description pro ceeds, the invention resides in the combination and arrangement of parts and in the details of construction hereinafter described and claimed, it being understood tha-t,.within the scope of what is claimed, changes in the precise embodiment of the invention shown can be made without departing from the spirit of the invention.

In the accompanying drawings c Figure 1 shows in top plan, a drafting instrument constructed in accordance with the invention; Figure 2 is a bottom plan; Figure 3 is a longitudinal section; Figure & is a cross section on the line H of Figure 2.

The device forming the subject matter of this application includes a protractor head 1 comprising a straight base 2 and a curved limb 3, an arm 1, of any desired length, projecting from the base 2. A cross piece 5 extends between the base 2 and the limb and constitutes, in effect a continuation of the arm 1.- The fiducial edge 6 of the arm 1 is alined with the fiducial edge 7 of the cross piece 5, and the fiducial edges 6 and 7 are disposed at right angles to the fiducial edge 8 of the base 2. The limb 3 is inscribed with degree scales 9 reading'in opposite directions from a zero point 10 alined with the fiducial edges 7 and 6 of the parts 5 and i. The base 2 is provided 'betweenthe base 2 and thearm 4. Areinforcement at this point is -important, because the tool, preferably'isfmade inrela-i 'tively large size for blackboardluse, and,

with scales 11 which read inopposite direc- I t1ons from a zero. point alined with the fiduclal edges 6 and 7 of the members 1 and o. The arm 4: has a scale l2 reading from a zero pointalined with the fiducial edge 8 of the base 2, the arm 4 having openings "14: coinciding with the unit gradu'ations of the scale 12, and ofsuflicient size, preferably to receive a piece of chalk.

r The arms is connected with the base 2 by an integrally formechhollow cup-shaped hub '15. This hub 15 is animp' ortant feature of the device. It forms a strongv connection at thersame time, must be made ligh-t. Since the tool I is intended primarilyfor useon "a blackboard in a school and is not handled ordinarilyby an engineer, "draftsman, or other person likely tofiexercise extreine 'care the device issubjected to hard use, and there is a very goodreasonfor reinforcing it, by means oiathe hub 15. The hub 15 terminates-inayreduced-neck 16 wherein a plunger 17*is mounted for right line reciprOcatiOn', the plunger being supplied at its outer end with a button 18. y A

compression spring 19 surroundsithe plunger 17, one end of the spring engaging the button 18, and the other end of the spring engaging the neck 16. Onthe inner end of the plunger 17, there is a securing element 20,such as a headed screw, retaining a resilient cup-shaped suction member 21,

preferably made of rubber, the size of the suction member being retracted into the hub 15 by the action'o-f the spring '19, the suction member will be housed within the hub. When the suction member is retracted, asaforesaid, the reduced tip 29 on the suction member engages such that when it is the inner surface of the hub 15 and spaces I the suctionmember from the inner surface of the hub. The suction member, therefore, does not tend to stick in the hub, but may be advanced, readily out of the hub, when pressure is applied to the button 18 of the plunger 17. The center 220i the suction coincide with the fiducialedges 6 and 8 of the members 4 and 2 and are located at the apex of the angle defined by the said edges. Consequently, the button [18 furnishes'can member 21 and the center of the button 18 important index whereby the suction memher 21 may be placed, approximately, at the desired point on the blackboard.

The base 2 is provided on its under side with a groove 23 and there is a like groove 24: in the under surface of the limb 2: Where the grooves 23 and 24 communicate, at the corners of the head 1, pads 25, made of felt or the like are seated and held. These particular parts 25 are subjected to more wear: than are. any of the parts hereinafter alludedrto, and since the parts 25. are sea-ted in; the communicating portions. of the grooves and 2.45, the parts will be held securely in place. The cross piece 5 may be extended across the groove 24; in-the limb 3, as shown at 26, this portion of; the cross piece carrying a, pad 2.7. Pads 28 may, be distributed along the arm. 4:. It; w-il'lbe understood,,however that all of the, parts may be located asdesired. The, function of the parts. is to prevent the tool from scratching the blackboard- In practical operation, the plunger 17 is thrust inwardly by means of the button 18, the spring 19 being compressed, and the suction member 21 acquiring a hold o-nthe blackboard. The tool, therefore, is mounted on the blackboard; for swinging movement andifja, piece of chalk be placed in one of thev openings: 4,. the circle or the are of a circle may be struck. By maki-n a mark on the blackboardcoincident wit the Zero point: 10- to serve as an index, the fi'duc-ial edge 63 of the. arm l. may be usedto. draw a radial line with, respect, to the. center 22, the instrument, therefore, being capable of use as-a= protractor; The fiducial edges 6 and 8 may be employed to draw lines at right angles to eachv other. Should it be desired to extend, beyond the center 22, a line drawn along the fiducial edge 6 of the arm l, the fiducial edge 7 of the cross piece 5 comes into-play.-

VVhat isclaimed is 1. A tool of the class described, including a protractorhead comprising a curved limb and a base, and an arm pro ecting from the base, the base-and the armhaving fiduci-al edges definine a right angle, av cup=shaped hub, joining t e arm; to the, base and reinforcing them at their point. of juncture, and a compressiblesuction member slidable in the hub and housed in the. hub when retracted.

2.. A device; of the class described, constructed as set forth in claim 1 and. further characterized; by the fact that. the center of the suction memberis located at the apex of said angle.

A tool of the class described, constructed as set forth-in claim 1, and further characterized by the provision of spring means for; retracting the suction member, the suction member including a reduced tip, which, cooperating with the hub, spaces the suction member from the hub when the suction member is' retracted.

In testimony that I claim the foregoing as my own, I have hereto aflixed signature in the presence of tWo witnesses.

NOBLE B. HUNT, RUTH Hat. 

